# This file is part of CherryPy <http://www.cherrypy.org/>
# -*- coding: utf-8 -*-
# vim:ts=4:sw=4:expandtab:fileencoding=utf-8

__doc__ = """Module auth_basic.py provides a CherryPy 3.x tool which implements
the server-side of HTTP Basic Access Authentication, as described in RFC 2617.

Example usage, using the built-in checkpassword_dict function which uses a dict
as the credentials store:

userpassdict = {'bird' : 'bebop', 'ornette' : 'wayout'}
checkpassword = cherrypy.lib.auth_basic.checkpassword_dict(userpassdict)
basic_auth = {'tools.auth_basic.on': True,
              'tools.auth_basic.realm': 'earth',
              'tools.auth_basic.checkpassword': checkpassword,
}
app_config = { '/' : basic_auth }
"""

__author__ = 'visteya'
__date__ = 'April 2009'

import binascii
import base64
import cherrypy


def checkpassword_dict(user_password_dict):
    """Returns a checkpassword function which checks credentials
    against a dictionary of the form: {username : password}.

    If you want a simple dictionary-based authentication scheme, use
    checkpassword_dict(my_credentials_dict) as the value for the
    checkpassword argument to basic_auth().
    """
    def checkpassword(realm, user, password):
        p = user_password_dict.get(user)
        return p and p == password or False

    return checkpassword


def basic_auth(realm, checkpassword, debug=False):
    """basic_auth is a CherryPy tool which hooks at before_handler to perform
    HTTP Basic Access Authentication, as specified in RFC 2617.

    If the request has an 'authorization' header with a 'Basic' scheme, this
    tool attempts to authenticate the credentials supplied in that header.  If
    the request has no 'authorization' header, or if it does but the scheme is
    not 'Basic', or if authentication fails, the tool sends a 401 response with
    a 'WWW-Authenticate' Basic header.

    Arguments:
    realm: a string containing the authentication realm.

    checkpassword: a callable which checks the authentication credentials.
        Its signature is checkpassword(realm, username, password). where
        username and password are the values obtained from the request's
        'authorization' header.  If authentication succeeds, checkpassword
        returns True, else it returns False.
    """
    
    if '"' in realm:
        raise ValueError('Realm cannot contain the " (quote) character.')
    request = cherrypy.serving.request
    
    auth_header = request.headers.get('authorization')
    if auth_header is not None:
        try:
            scheme, params = auth_header.split(' ', 1)
            if scheme.lower() == 'basic':
                # since CherryPy claims compability with Python 2.3, we must use
                # the legacy API of base64
                username_password = base64.decodestring(params)
                username, password = username_password.split(':', 1)
                if checkpassword(realm, username, password):
                    if debug:
                        cherrypy.log('Auth succeeded', 'TOOLS.AUTH_BASIC')
                    request.login = username
                    return # successful authentication
        except (ValueError, binascii.Error): # split() error, base64.decodestring() error
            raise cherrypy.HTTPError(400, 'Bad Request')
    
    # Respond with 401 status and a WWW-Authenticate header
    cherrypy.serving.response.headers['www-authenticate'] = 'Basic realm="%s"' % realm
    raise cherrypy.HTTPError(401, "You are not authorized to access that resource")

